Balloon angioplasty is a nonsurgical method of clearing coronary and other arteries, blocked by atherosclerotic plaque, fibrous and fatty deposits on the walls of arteries. A catheter with a balloon-like tip is threaded up from the arm or groin through the artery until it reaches the blocked area. The balloon is then inflated, flattening the plaque and increasing the diameter of the blood vessel opening. The arterial passage is thus widened. A wide variety of catheters have been developed in the prior art for percutaneous transluminal coronary or peripheral vascular applications. One example is a balloon dilatation catheter for performing percutaneous transluminal coronary angioplasty, which is well known in the art.
An artery is one of the tube-shaped blood vessels that carry blood away from a heart to the body's tissues and organs. An artery is made up of an outer fibrous layer, a smooth muscle layer, a connecting tissue layer, and the inner lining cells. If arterial walls become hardened due to the accumulation of fatty substances, then blood flow can be diminished. Accumulation of fatty substances occurs most often at the site of bifurcated branches where the separation of flows favors the deposition of fatty substances. Hardening of the arteries, or loss of vessel elasticity, is termed arteriosclerosis while fatty deposit build-up is termed atherosclerosis. Atherosclerosis and its complications are a major cause of death in the United States. Heart and brain diseases are often the direct result of this accumulation of fatty substances that impair the arteries' ability to nourish vital body organs.
There are limitations, however, to this technique's application, depending on the extent of the disease, the blood flow through the artery, and the part of the anatomy and the particular vessels involved. Prior art vascular dilatation balloons are axially straight and are most effective in a relatively straight vessel. However, plaque build-up and/or severe stenosis mostly occur at the point of vessel bifurcation where the blood flow is turbulent and the deposition of fatty substances is most likely. Recently, a newer technique was developed to perform a balloon dilatation procedure at the bifurcated region by inserting two balloons of different sizes sequentially into a first vessel and a second bifurcated vessel, respectively. However, the procedure of double-balloon sequential dilatations is not very successful in treating the stenosis. When a first vessel is dilated by a first balloon, the inner vessel wall of the first vessel at the bifurcation region tends to temporarily recede because of the balloon's pushing. Once the first balloon is deflated, the inner vessel wall of that first vessel at the bifurcation region bounces back and the dilatation effectiveness is compromised.
The bifurcated balloon is also useful to deploy a bifurcated stent at the bifurcated region of the blood vessels as a further treatment to the stenotic tissues. When a clogged artery is widened, the plaque is broken up and the underlying collagen or damaged endothelium is exposed to the blood flow. Collagen has a pro-thrombotic property, which is a part of the body healing process. Unless the collagen or the damaged endothelium is passivated or modulated, the chance for blood vessel clotting as well as restenosis still exists. Moderate heat is known to tighten and shrink the collagen tissue as illustrated in U.S. Pat. No. 5,456,662 and U.S. Pat. No. 5,546,954. It is also clinically verified that thermal energy is capable of denaturing the tissue and modulating the collagenous molecules in such a way that treated tissue becomes more resilient ("The Next Wave in Minimally Invasive Surgery" MD&DI pp. 36-44, August 1998). Therefore, it becomes imperative to post-treat vessel walls after the walls are treated with angioplasty and/or stenting procedures.
One method of reducing the size of cellular tissues in situ has been used in the treatment of many diseases, or as an adjunct to surgical removal procedures. This method applies appropriate heat to the tissues, and causes them to shrink and tighten. RF therapeutic protocol has been proven to be highly effective when used by electrophysiologists for the treatment of tachycardia; by neurosurgeons for the treatment of Parkinson's disease; and by neurosurgeons and anesthetists for other RF procedures such as Gasserian ganglionectomy for trigeminal neuralgia and percutaneous cervical cordotomy for intractable pains. Radiofrequency treatment, which exposes a patient to minimal side effects and risks, is generally performed after a stent is deployed in a body lumen.
Therefore there exists a need in the art for a vascular dilatation catheter to have a bifurcated balloon to inflate the bifurcated region of the two vessels simultaneously. By performing a procedure using a dilatation catheter having a bifurcated balloon, the stenotic region at the bifurcation zone can be effectively treated.